It more often means wanted but it can mean tried. http://context.reverso.net/translation/spanish-english/quise
According to my grammar book, "The preterite of querer + infinitive is peculiar in that out of context it is ambiguous."
Preterit can also mean that you gave up wanting because you weren't able to get what you wanted somehow. Maybe it started pouring rain, maybe the castle was closed, maybe you were tired? The wanting ended, but we don't know why for sure.
Yes, I wrote "I chose to walk to the castle" implying that I wanted to and no longer wanted to (since I did walk).
The preterite implies an ending to the wanting, something which isn't expressed by the translation "I wanted to walk to the castle", but is by both I tried, and I chose.
Both can be translated as 'I wanted to walk to the castle' but 'quería caminar al castillo' "sounds" more like you are just stating that you had the desire to do the action while 'quise' kind of implies that you had the intention to actually do it, and maybe you even tried to and failed, or you just lost interest in doing it. But, again, in certain context both sentences could be used nearly indifferently. I hope it helped :)
No, in the preterit "Yo quise" and "él quiso" http://conjugator.reverso.net/conjugation-spanish-verb-querer.html
The safest thing to do is to translate both as wanted because the implications aren't always clear without context.
quería = Someone wanted to do something but the imperfect doesn't tell you if anything was done or not
quiso = Someone wanted to do something and can meaning either of the following. Out of context and with no other clues, it's ambiguous and you may not know which meaning is intended.
It often means that someone wanted to do something and meant to do it or tried to do it but wasn't able to do it for some reason.
However, it can sometimes mean that someone wanted to do something and DID do it, which is the totally opposite meaning!